Cake knife



FIG. 1 is a perspective view of a cake knife, showing my new design;

FIG. 2 is a front view thereof with a rear view being the mirror image;

FIG. 3 is a left side view thereof with a right side view being the mirror image;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof. 

The ornamental design for a cake knife, as shown and described. 